Here are some things you might find useful:

• HPFSPm v1.2 -- a PM (graphical) interface for HPFSRem by TIME Soft (Stefano Zamprogno)
• The Iomega Zip and Jaz drivers (is a newer version out now?)

Other removable HPFS solutions (please don't ask me for help -- I don't know how they work and didn't make them):

• Lockdrive, a filter that can make removable drives look like fixed ones to OS/2 -- may help Zip and Jaz users who can't use the OAD driver. It comes from ftp.leo.org.
• SCSI removability software for Iomega and SyQuest drives. I don't know how well this one works (I use an IDE SyQuest), but you're welcome to try. Also from ftp.leo.org.