Triangle test glasses?

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Triangle test glasses?

I know frosted glasses are preferred, but I don't have any of those.  I've built up a stockpile of taster glasses for flights for my friends that come over, but of course they are all clear.

Does anyone have suggestions on best glasses for triangle tests?  Links to Amazon are especially appreciated(Drew/Denny-you guys should have an Amazon affiliate link.)

I did find some 10oz red solo cups on Amazon, but wondered what other people were using.