Cannot read headshape for Yokogawa recordings

Dear Francois & Brainstorm Team:

Following up on this: I have a Yokogawa dataset without individual .sfp or .elp files and the data was not exported from the acquisition system as described in the tutorial. So, ultimately, I only have .con and .mrk files for each of the runs as well as a subject MRI for each of the subjects. Is there a way - even though of course much less accurate - to still perform source reconstruction for these files ?
Thank you very much in advance!

Bahne