So, when I got on to an DSLR, I decided to build another close up lens which fits my Canon zoom EF 28-135.
I wanted a very good quality for it, and of course it should be an aspherical lens, to reduce chromatic aberrations at borders of the image. I decided to go asking to my usual good optical shop here in Milan for a glasses' lens. So he provided for this great quality aspherical lens, of course it's uncutted.
I'm not able to give you the detailed characteristics of it, but if you explain to your optic your pourposes he should make the best choice for you. [UPDATE: I've found the envelope, following are the characteristics of my lens: DX OP CR.39 1,5 ASPHERA 3, Sph +500 ,Cyl + 0]
Ah, mandarin is only to keep the lens up... and to catch your interest of course ;-)
Step 1: The rings
You can find very cheap filters and adaptors on eBay, there are some steps in the available diameters (24, 27, 30.5, 37, 40.5, 43, 46, 49, 52, 55, 58, 62, 67, 72, 77, 82, 86mm), so take note of them before going to ask for the lens. You also can find adaptors to reduce or enlarge diameter of your lens, but remember that the more you reduce it, the more you loose luminosity.