Unfortunately you can't buy less then 7 meters unless you visit a yard. BMW part number is 61120142318
. You can easily cut it, you may need more part like 61136901847 and 61136901846 basically many but all part you can find in the link I made to the first part number above.
X5 40d M Sports - Fully loaded, 7 seats.
Sold 535d LCI, Xenon Adaptive Headlights, ACC 2 (Stop and Go), LDW/TLC
Retrofits M5 heated/lumbar/memory and active backrest adjustment seats, rear heated and folding g seats, SAT Shifter, paddles (SA2TB), HUD, Rear blinds, Electric steering column, SA430 Folding and EC Mirrors, High Beam Assist, CIC, COMBOX Telematics.