Affixable hard-tops were available for E36 convertibles (aftermarket, I believe). But they were one-piece, large, cumbersome dealies, not retractable/folding.
Tbh never understood hardtop options for cars You are basically getting 0 wind hair of coupe with the noodle body strength of convertible
Similar to E46 hard tops, we used to have an LCI 325i cabrio and it retained the soft top, although we saw loads of them with the aftermarket hard tops, and not gonna lie, they look terrible. Probably for the best that they don't get added haha