This is something I looked into doing for my Rem 700 in 308. I found a lot of information at the forums at snipershide.com and snipercentral.com. Dont know your caliber, so you may be a lot more limited than what I've looked into. Regretfully, they're all pretty much in the same price range.
Some of the manufacturers are Badger, Seekins, Surgeon, V-Bull Precision, CDI, and of course HS Precision.
Basically, except for the HS precision ones, all of them seem to be pretty good quality. The HS negatives seem to be more based on preconceptions from someone elses comments, not actual first hand experience, so I'm not sure how much I believe those. Compared to the others, the HS one does look a bit on the flimsy side though...
The biggest difference between them seems to be the magazine they use, as some use an AI mag (about $70 each), and some use their own mag.
I dont know why, but for some reason I always go back to the Badger one when looking at it. Maybe its just because they're a bigger company or their bolt knob is so popular, or something else. No clue. The HS does seem to support the biggest range of calibers, as well as both long and short action rifles. I think it might come down to just the type of mag release you want.
Some links to to the manufacturers sites.http://www.badgerordnance.com/productgroup.php?id=accessories#http://www.seekinsprecision.com/index_p.php?p=dmaghttp://www.surgeonrifles.com/products/accessories/?module=products&product_id=154http://www.vbullprecision.com/
(site is being updated) http://www.jwprecision.ca/mat.html
is a review by one of their resellers for the Savage version so you can at least see what it looks likehttp://cdiprecisiongunworks.com/c1/index.php?option=com_content&task=view&id=7&Itemid=27http://www.hsprecision.com/shop/detachable-magazines