You may have to go straight to Garmin as I'm not finding any parts either. https://my.garmin.com/rma/repair/repairLanding.htm
Just remember you can get the whole thing for $105 on eBay, get what part you need and sell the rest: http://www.ebay.com/itm/Garmin-010-N0779-00-Garmin-eTrex-Legend-H-NOH-Remanufactured-/130709682406?pt=LH_DefaultDomain_0&hash=item1e6ee778e6#ht_3433wt_1141