You won't find them used as they are typically sold with the bumper cover by breakers on Ebay and other places. Just pony up the $30 and move on. There are MUCH worse gouges for BMW. Example, I just bought an E61 5 series wagon and it needs the hydraulic lift strut for the rear hatch. BMW is the only brand offered and lowest price I've found is $922!!! So yeah... it could be worse.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)