Samsung NX and the Rollei QBM lens (Schneider, Zeiss, Rolleinar...)

Depends on your budget, anything with macro on it will cost more. Do a search on ebay with "macro 55 2.8" and you'll find a number of macro lens in different mount. Choose the mount that you like to expand on. Normally, Canon FD mount is the cheapest because not many camera has adapter for that, but there is one for NX-FD in ebay.  M42 mount has loads of excellent lens but they normally cost more. If all you need is close focus, then try to find the cheap Pentacon 50/f1.8, very good value.