jspilane's right about cost. a 55 micro nikkor & inexpensive body for about $100. OR.
Find a Visoflex, a focusing adapter, adapter tube & lens head. I'd guess that without a lens you're looking at around $300. Oh, oh, pretty soon you'll be talking serious money.
BUT!
Leica did have a number of close up devices like:
NOOKY, NOOKY-HESUM, SOOKY, UOORF, BOKUM, SOOKY-M, ADVOO, SOOGZ, SNHOO, OMIFO.
These things are all for specific lenses. But I love the catalog numbers, Some of them are similar to sounds my dogs make.