Is there a way to permanently shrink pants a bit?

UGH! So I don’t know if I’ve lost a little bit of weight, but either way it’s negligible, however I notice that many of my pairs of pants are just slightly too big and they look sloppy….and I am not one to spend money on clothing, all of these pants have come from thrift stores and one pair specifically, these light purple jeans I found not too long ago, are just awesome, and I’d really like to be able to continue wearing them. But they are just slightly too large. When I immediately take them out of the dryer and put them on, perfect. But 5 minutes later they’re a size larger and I’m annoyed. They aren’t stretch or anything.

So, maybe this is a dumb question, but is there any way I can get them to stay that smallest size, the size they are right after being washed? This would really be helpful to my wallet. THank you.