I've got a 40mW, 488nm SLM Spectra Physics Cyan laser on eBay right now.
http://www.ebay.com/itm/111186337584
It's only got around 1000 hours and is making a stable 45mW. SP doesn't sell these any more and the specs in the manual say single frequency, but don't include bandwidth or coherence length. I'm willing to guarantee it's got at least 1m coherence length for any holographers interested in giving it a shot. Probably the cheapest SLM blue laser you're going to see for a while