Just get any 1.44 and use a tape to cover left hole :-)
HIGHLY recommend AGAINST this. If you're using 880k (DSDD) drives use the proper disks otherwise you run the very real risk of losing data.
The quality of 1.44MB disks decreased drastically in the decade or so up to their final demise, which increased failure rates in proper drives let alone the magnetic flux issues with using HD in a DD drive.
You can find NOS around eBay. I have amassed quite a stash, myself, and my consider parting with some of them soon... once I get to them (reorganizing the office... can't find my @ss with a spotlight right now.)