Yes, a perfect time to do this now that you've got the air distribution box opened up. I'm a bit jealous as I've got one or more failed bellows in both my 940s. You'll note you have two different ones -one has a double action and the most likely to fail. These have long been NLA in the Volvo parts chain, so don't even bother waiting for a reply from parts houses that still list them for possible order.

There's a crude bypass you can do by plugging one port and its hose, but it's less than satisfactory and that bypass didn't last long in the one 940 I did a few years ago.

If you search around hard enough, someone posted somewhere of finding a GM Delphi one that can be adapted, mostly it was just the mounting as I recall. I don't know if that part is still available.

.......Ah, found it here on Turbobricks!!
https://turbobricks.com/index.php?threads/part-for-2-port-ac-delco-or-a-c-t-s-ltd-vacuum-bellows.329764/

Failing that, I'd be very tempted to find a yard that might be willing to sawzall out a bunch of those for you to try.

Keep us posted here on your progress as that project is betting higher on my do-list, especially in winter.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now