I was stumbling through the net yesterday and came across this online store, Ben Franklin. I think they're located in Wisconsin. Anyway, among their inventory of art supplies was a large bottle of water miscable linseed oil medium made by Reeves.
Link:
http://tinyurl.com/d3rk3kz
Disclaimers: I've not bought from Ben Franklin before, or used this product. I'm just pointing it out since it's a very good price. That's about half what Blick charges for Artisan linseed oil medium. I've avoided Reeves' paints since they seem to be student grade, but that shouldn't affect their mediums. If anyone has tried this or wants to, I'd be curious how well it works out. If any one has bought things from this place before, I'd also like to hear about that since they have a good selection of stuff.