smooth on wil cure at room temp if you give it a while.
I think any top quality slow cure epoxy should be fine. I wouldn't use the walmart or hardware store special .... but a high quality slow set epoxy ... i can't imagine it's not going to be ok.
with that said ... it won't be cheaper than smooth on, so unless you're sitting on a stash of 24hr cure west systems epoxy, I'd order a bit of smooth on