Those posting are very much stating the reality of the situation. Yes you can cut your own gobos. Even a excellent set of posts to stagecraft on more ways to do this than posted that could be expected to have more long term results.
Still in stating this possibility and ability to do so, all it seem compare normal cutable metal
thickness in it's ability to withstand heat over that of tinfoil, and in carving it, it's lack of refinement and material workability in also withstanding a more perminant sense of heat.
Perhaps the classic pie tin or similar types of metal can be cut to your
image and it will work. Perhaps in doing so, making multiple copies of the patterns will be a good idea in just replacing them before they burn up each night. Could be a good solution in fact.
On the other
hand, while initial cost is a factor in custom
gobo, the savings in time labor and it simply not burning up will often be worth it to pay for the higher priced custom
gobo. This if not even glass
gobo nobody would attempt in being at times better yet.