Automotive patches tend to be fairly thick. Usable but thick. A lifetime supply
of patches is available in boxes of 100 made in Germany is sold by such as
AEBike for $15-18/100 depending on size. These are round 15 or 20mm in diameter.
8oz cans of suitable cement are in the Wmart auto dept and last 5yrs or so til they
get too thick to use. I keep the little sealed tubes of glue in the bike packs for
remote use on the road. I find it helpful to keep an old rim around with rim strip and
mount the repaired tubes on the rim for a few days to make sure they hold air.
This also tends to prestretch new tires making them easier to mount later.