I used to use a Minolta Rokkor 50mm f3.5 macro lens on adapted bellows.
Was very sharp back when I used SR-T film bodies on its own, and held up well on my EOS cameras, though was very dark through the viewfinder...
This is something to bear in mind... make sure any lens you buy stops down when the aperture is changed on the lens, without a coupling pin or stop down release. Some manual lenses stay wide open unless they are mounted with the correct trigger pin (like MD lenses)
Your best bet may acutally be an enlarger lens, failing that NOVOFLEX used to make reversing rings that retains comms with the camera.
To behonest though, I much prefer using a dedicated macro lens with a manfrotto 454 plate.
2nd hand values on the Sigma 50mm EX f2.8 and Canon 50mm f2.5 or even the tamron 90mm aren't that much more than what you'll spend on tubes and old lenses etc.
Really for macro you want max aperture preview as your shooting aperture may be so small that it's impossible to use the live view or the viewfinder, especially as live view doesn't always wprk properly with non-comm lenses.