I bought the Tomtoc 13 inch (not 13-13.3 as it is larger) sleeve off of Amazon - https://www.amazon.com/gp/product/B01HCV206Q/. The internal dimensions are pretty close to the Pixelbook. There is some space on either side of the Pixelbook when in the sleeve which I hope to make use of when the Pixelbook Pen clip comes out and I clip it to the side of the device.
Pretty pleased with it. It's not rigid like the Bellroy but it looks decent and you can't argue with $20. Plus, it's got a pocket on the front that I use to store my Kindle and any cables I might need.
The Tomtoc sleeves on Amazon are a common favorite around here for the price. I've been using one since the summer and have been really happy with it. The price was 17 bucks when I got mine. I got the 13 inch and it was a little snug at first, but now it fits perfectly. I get a lot of compliments on it and I love that it closes with magnets.
I just bought this one actually, it’s arriving tomorrow! It’s worth checking out.
TomToc Slim Laptop Sleeve for New MacBook Air 13-inch with Retina Display and 13 Inch MacBook Pro with USB-C Leather Envelope Case: https://www.amazon.com/dp/B01HCV206Q/ref=cm_sw_r_cp_api_i_6DHoDbDM5A07Y
I've got the 15" version of this one https://www.amazon.ca/gp/product/B01HCV206Q/ref=oh_aui_detailpage_o00_s00?ie=UTF8&th=1
Not an issue at all placing my laptop on the sleeve because of how the magnets are positioned. I've been using it for 3 weeks without any issues at all. Opening and closing it is very slick with the magnets and the sleeve itself is very nice quality.
Only 20 bucks.. This is the 13" model for the MacBook Pro (not the 13.3" size)
I ended up buying this: https://www.amazon.com/gp/product/B01HCV206Q/ref=od_aui_detailpages00?ie=UTF8&psc=1
I personally like this one https://www.amazon.com/gp/product/B01HCV206Q/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
It gives you access to both usb-c ports so you can charge it without pulling it out of the sleeve
I purchased this one: https://www.amazon.com/dp/B01HCV206Q/ref=cm_sw_r_cp_dp_T2_yI4lzbHF055NS
Has been pretty good so far. Great fit, and the magnetic flap is a huge plus because I didn't want a zipper.