Headrests are tough to choose without fit testing in person, but the CLATINA Mellet is generally a solid choice - lots of adjustability for the price. https://www.amazon.com/dp/B07DVLWZSK/
But over 12 hours a day... that's killing you! Perhaps consider getting a sit-stand desk instead (one that adjusts down to 25" or lower); switching postures between sitting and standing is healthier overall than just sitting, and will make sitting in your Markus more bearable.
I was looking for a Mesh chair and spent a lot of time looking. I ended up settling on this chair. BUT they have both mesh and fabric. A lot of people recommend used high end chairs but I was looking when everyone was starting to work remotely and even used or disconnected items in my area were way more than I felt paying
CLATINA Ergonomic High Swivel Executive Chair with Adjustable Height Head 3D Arm Rest Lumbar Support and Upholstered Back for Home Office Gray https://www.amazon.com/dp/B07DVLWZSK/ref=cm_sw_r_apan_glt_fabc_HBN8YVADCFJMHJ4ZD56Q?psc=1
I bought this one more than year ago and was immediately impressed how well built it was and pretty comfortable
CLATINA Ergonomic High Swivel Executive Chair with Adjustable Height Head 3D Arm Rest Lumbar Support and Upholstered Back for Home Office BIFMA Certified Gray https://www.amazon.com/dp/B07DVLWZSK/ref=cm_sw_r_cp_api_i_rfl.Db8SEDE0T
Clatina Mellet is a decent leap impersonator. Of course long term durability may not be as good but has been great for me since 1/2021 and mostly comparable to the leap v2 at work: $230 with headrest on Amazon. Also Walmart and eBay I think
link to info dump comment on Clatina Mellet
Edit: this Amazon link is cheaper for some reason:
CLATINA Ergonomic High Swivel Executive Chair with Adjustable Height Head 3D Arm Rest Lumbar Support and Upholstered Back for Home Office Gray https://www.amazon.com/dp/B07DVLWZSK/ref=cm_sw_r_cp_api_glt_fabc_71SM47J4A2XMV1YRM2QJ
A great option under $250 is the Clatina Mellet. For $20 over your budget, you could get the Union and Scale Ayalon (made by Eurotech, supposedly some kind of chimera of a Vera base and Exchange back).
Staples Canada has this Raynor chair which appears to be the same as the well-regarded Workpro 4000. If you could order from Amazon USA, you could get the Clatina Mellet. For whatever reason, it's not on Canadian Amazon.
Other than that, if you can find a used office furniture store in your area and your workplace would accept that, it would be a great idea to check one out and see what kind of used high-end chairs you could find.
Headrests are tough to choose without fit testing in person, but the CLATINA Mellet is generally a solid choice - lots of adjustability for the price. https://www.amazon.com/dp/B07DVLWZSK/
Canadians can order from Amazon US, right? If you can, you could order the Clatina Mellet or the Sidiz T50.
If you have an IKEA near you, try sitting in the Matchspel. It's like a cheaper version of the Jarvfjallet, but with softer seat foam, so many people like it more.
If you could forgo the headrest, you could get a refurbished Steelcase Leap V2, which is the stone cold favorite chair of many on here. Ideally, if you could find a used furniture dealer in your area, you could try out multiple high-end chairs in person.
From what I’ve read, secret labs are mainly just gaming chairs.
I wasn’t able to find a used or refurbished steelcase in my area or budget. I use a steelcase leap v2 at work and found the Clatina Mellet to be an acceptable budget stand in. Seems to fit people 5’1” to 6’1” well per Amazon reviews and up to 275 lbs.
comment with gathered summary of information for reference
Canadian Amazon listing:
CLATINA Ergonomic High Swivel Executive Chair with Adjustable Height Head 3D Arm Rest Lumbar Support and Upholstered Back for Home Office (Gray) https://www.amazon.ca/dp/B07DVLWZSK/ref=cm_sw_r_cp_api_glt_i_5FGN8CG29HM4EPMZWBEH?psc=1
Good luck finding something that fits your needs