Yes, you can buy the small case separately, in ABS plastic either with a clear lid or an opaque lid: search the internet for RP1095 or RP1095C and you’ll find multiple vendors.
There’s also a new version with mounting flange feet if you’re planning to mount the case somewhere where having the flange would be helpful. Those are model RP1095BF and RP1095BFC
And if you’re going to be mounting these boxes out in the sun for multiple years, you might want to use their new polycarbonate plastic versions instead of ABS. They’re a little more expensive but will hold up longer if you’re using them by themselves instead of inside a Pelican case. They are models RP1090, RP1090C, RP1090BF, AND RP1090BFC
The Mayfly vertical microSD memory card adapter boards are currently not available separately, but we do offer 5-piece set of them in our EnviroDIY shop.