Get an under-the-lens swing-away filter holder and some ruby-lith or the like, or find an alternative way to position your paper.

How about just using some blue painters tape to mark where the corners of the print should go? Position these with white enlarger light and with a wide-open aperture. Then dial-in your filtration, stop down and position your paper. Or, get some sheet steel and magnetic strips to hold your paper (used in conjunction with the red filter, this is your best non-easel solution IMO).

Best,

Doremus