One you'd get from a head shop or Amazon. I get mine in packs of 50 like this
Made in the USA - 50 5/8"(.625) 304 Stainless Steel Premium Pipe Screen Filters https://www.amazon.com/dp/B01DTDWOC6/ref=cm\_sw\_r\_cp\_apa\_pQgGBbHG8XB5H
Whew.
I understand your concerns with a torch - though the too hot vapor thing isn't really something that happens. But, you mentioned joint problems, the thing with the Dynavaps is that almost all heat sources will require you to spin it to get even heating and not combust, and a torch is the fastest way to do that.
So. Dynavap, it's a great vape, but in a nutshell, without a good heating source you're gonna have a bad time. There are options, though in my experience matches, candles, Zippos, etc just make it extremely frustrating, it takes so long to heat up. And you'll be spinning forever!
You can (and should) save a ton of $$ and buy one of these - https://www.amazon.com/Dental-Power-Infrared-Electronic-Induction/dp/B0114AD8TO
With that induction heater (which I have and use regularly) you don't have to spin, you don't have to push hard, you just set the Dynavap in the hole, Hold it there, and it heats up - when it clicks it's ready.
Good luck homie. Hope that helps!