>>5010543I didn't, so I went on a little pod hunt.
Orange is easy to get by selecting for lack of pigment, but actual red is very rare.
Here's the reddest (but still mostly orange) isopods I could find. The reasonably available ones range from ~$15-$50 for 10, to ~$150-$600 for the mythic Actually Red isopods.
Prices and availability vary a lot, so you may find some of these way cheaper on a lucky day, but I doubt the bottom ones will be anywhere near common or reasonably priced for years.
Most of these are just picking your favorite orange desu. If you don't mind that, your options are unlimited and you can simply pick up some Powder Orange from a brick and mortar pet shop for like $10.