Hi just found this on the Bilstein site, it looks like it is designed like that so you can fit 'Shock Boots'
http://www.bilsteinus.com/Bil_OR_shocks_bro.pdf
You might get away with a new collar, or if you can get to a garage see if they can weld a new nut on the collar so hopefully that will keep you going till you can get replacements
Kind regards
Mike