Precision Wargames Supplies now do steel bases with rounded corners.
I have long been a fan of steel bases because they are thin, strong and their lowest possible centre of gravity means less damage from "knocking over" and if they fall, they always land base down and figures up. They also work well with magnetised trays and boxes.
I also like bases with rounded corners so when I asked the proprietor Ian if he would do them he did, as a "special". Admittedly not a cheap option but the more you buy the cheaper they get. Check them out here:-
https://precisionwargamessupplies.rf.gd/steel-bases.html