The front ring is the Leica 39mm to M42 adapter (7844), and the bigger one is M42 helicoid (7842). The both are
available from TOMY company in Japan. This 7842 helicoid has 16mm to 26mm thickness, in order to attain infinity
focus you should obtain M42 helicoid (7840), which has 12mm to 19mm adjustable thickness. Although I give you
the company's home page address in here http://www.tomytec.co.jp/borg/index.php , I am not sure that they can
deal with foreigners. You can get these helicoids from eBay, the prices are a bit better (means cheaper @ eBay).
(The lens was $150 in Tokyo, Oasis ring cost ~$40 and the helicoid was $130 in Tokyo, the total cost is ~$320.)
(The same helicoid from eBay is normally around $70, so you can make the same thing much cheaper these days.)
Cut off the helical from the optical block by a hacksaw, before that the optics were wrapped around with plastic film.