Saw this pattern 1908 helve carrier on eBay a while back which went for $300...
http://www.ebay.com/itm/BRITISH-ARMY-1908-PATTERN-WEB-EQUIPMENT-HELVE-HOLDER-/131351591816?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2047675.l2557&nma=true&si=fZlHM47Qftc7emBmPBAoaFh%252BQnM%253D&orig_cvip=true&rt=nc
If you look closely, it is clearly 'made up' from two common items, an original 1918 P08 support strap and a P37 waterbottle carrier!
http://www.ebay.com/itm/BRITISH-ARMY-1908-PATTERN-WEB-EQUIPMENT-HELVE-HOLDER-/131351591816?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2047675.l2557&nma=true&si=fZlHM47Qftc7emBmPBAoaFh%252BQnM%253D&orig_cvip=true&rt=nc
If you look closely, it is clearly 'made up' from two common items, an original 1918 P08 support strap and a P37 waterbottle carrier!