headlight adjusters

Hi all, can anyone give me any pointers regarding the headlight adjusters on a 200tdi, i've managed to obtain a couple of second hand units to replace my badly corroded ones. (the idea is to upgrade one day to 300 tdi)the adjusters on the second hand units don't seem to have the knurled knobs my present units have.
is there a replacement knob assembly available or can adjustment be made with some other botch

those orange bits just pull off/ push on.

thanks mad hat man, going to pop out now & douse the the adjusters with penetrating oil & hope for the best. if it was not for the plastic bits on the studs i'd be tempted to use a bit of heat but i think i will have to be patient on this occasion.