Unusual for me but last year I tried to save money and bought a 'fake' Invisible Zipper Foot, think it was this one
www.amazon.co.uk/dp/B00HRYENVE/ref=pd_lpo_sbs_dp_ss_2?pf_rd_p=569136327&pf_rd_s=lpo-top-stripe&pf_rd_t=201&pf_rd_i=B0096DYFP8&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_r=1H3GWQTWSY49VGAKB0QZ
It didn't work - the needle hole was in the wrong place for one of the sides so I replaced it with a proper Bernina foot.
Might work on one of the older models listed (mine is a new 1008).
I have just found it in my foot box and would be happy to post it to someone who might like it if you think it will fit your machine.