KOY if you want cp-like beaters just get CP Or Svennsson on sale. The leather lining will make them last, and you'll actually be able to "beat" on them without worrying. If you want canvas, get something cheap, but be aware that they'll fall apart. There are a bunch of classic Nike court shoes around that I'm sure RFX can show you. Or get some surplus army trainers, which are actually pretty durable if you don't count the insole.
I've taken to wearing tshirts all day every day. Grabbed a collared shirt today and I was all like "what the fuck are these buttons doing on my shirt". Really it makes no sense unless you're wearing a tie, which itself makes no sense either.