Saw some in the last few days as am about to change tailgate.
Can't find the link but thought it was someone selling new stainless on ebay specially labelled for T25 tailgate.
Just tried searching for that and found this instead
http://www.vwheritage.com/vw_spares_Scr ... 461637.htm
Before trying to remove them, make sure there is no crap inside the allen key slot, get the allen bit that fits a socket and fit it in the bolt. Then give it a whack with a hammer and listen to the rust inside your roof box sections crumble off! Now put the socket on and with luck it will come free without mashing the slot in the bolt. My bolts look as thought they will be good enough to reuse.
E D I T: found in my brower history the ebay ones
http://www.ebay.co.uk/itm/T25-Wedge-Sta ... 4897.l4275