Thanks for the advise, my SIL and I are checking CL every day for a replacement. Though the fix is clever because of the amount of stress I have on it I'm worried that it will fail and send parts flying injuring me or someone else. I have some 2 inch vinyl tape I may wrap around it.
BTW the vise that broke is a 5 inch and the other that needs restored is a 4 inch.
Sled
As you have yourself stated the chances of fixed vise falling apart again and possible injuring you are indeed very high and honestly I am not sure if vinyl tape will be of much help.
If these were my vises until I could find a good replacement, this is what I would do (others might or might not agree and might have much better ideas).
The broken vise is done for, so I would not hesitate to use it as a parts vise to restore the older D44 4" vise. Also the older D44 as you have pointed out is essentially useless too (due to issue with jaw inserts). Additionally both vises are not high quality and expensive. So your risk of an attempt to make one whole vise from the two is not very high.
Since the broken vise has 5" jaw inserts I would remove these and shorten them to 4" (1/2" from each side). This can be done using a range of tools, such as band saw, or even a hack saw or frankly a grinder or angle grinder. The good news and bad news is that the broken vise being a lower end vise, its inserts are probably not that hardened and this is also true of the older D44, so there is no loss of quality here. Also it should be fairly easy to drill, grind/cut them
If the holes of the inserts do not lineup with the holes in the older vises jaws, drill new holes (as long as they are not too close to the existing holes in the inserts). Finally if the height does not match (the broken vise 5" inserts might be taller) I would simply grind them down as the difference in height should not be that much.
In fact it might be easiest, if you were to first take care of the holes lining up, you could then put the inserts on the old vise (symmetrically, so that the inserts protrude 1/2" from each side) and then use an angle grinder on each side to shorten the inserts flush with sides of the jaws. And then if necessary (ie there is a insert height difference) you do the same to top of the inserts.
Some might say just leave the inserts protruding 1/2" from each side but since these 1/2" ends have no shelf support, it is possible that they will break during usage and ruin the entire insert(s). So personally I would try to take care any width as well as height differences.
And hopefully some time soon you will find a better replacement but meanwhile you have one reasonably usable vise.
As I said this is what I would do but then again I have done crazier things and experiments as long as they are not costly and upside risks are not too high (which I think is applicable to your current situation)