Cheap way is to get a pair of sweat pants that run a bit tight down by the legs. If not, use Velcro to keep pants from getting caught in the chain. My other suggestion is to wear a pair of BMX pants
https://planetcyclery.com/troy-lee-designs-sprint-pants-burgundy?gad_source=1
I wear Spandex knicker (some has a flees type fabric on the interior) to keep warm. It doesn't get that cold here. You can wear your shorts on top of that. You will look just like some of the postal delivery man with that tights under their shorts.
Check it out, you may like it. I suggest tights under your shorts. They have a padding and go commando so there's no whitey-tighty going up your butt or bunching up under there. It makes riding so much more enjoyable.
these will work for you under shorts. Something similar will do it doesn't have to be this brand. I happen to like then and found them comfortable. The bib will keep them from showing crack in front of the pretty girls at the beach
https://www.performancebike.com/castelli-entrata-bib-tights-belgian-blue-w-chamois-xl-m20524424-5/p1519145?v=1505509