They're really common and any music shop carries them. When I owned a little music shop we carried the Boss loopers in the 1990s but I haven't used one in decades. I'm sure they've improved a lot but good ones are pricey. Just realize you need a pickup in your guitar and must be plugged into an amp to use one so it's not really for acoustic playing. If you just want to solo over patterns, you can quickly record loops with a mic in Garage Band/Logic Pro and practice soloing without amping up.
I play a Tiny Tenor 6 so I look taller on stage!