Nah - they still exist. And you can get the petrifilm ones from them pretty easy. Your local laboratory supply shop will have them available (3M partner distributors anyway). Like these.
They have a whole start-up kit.
I’d make sure to have an incubator (or any other enclosed temperature and humidity controlling device) that you can monitor temperature and humidity in.
Plus also a plate counter - which you can make yourself…or you can get one for like $500-1500 dollars depending on the bells and whistles. This makes it a lot easier to do the counting - and you can do the counts more than once. I know people who count without one, using a permanent marker or something…makes it super hard to recount or show the plate to someone after.