Double possession dilemma: should I say “your” or “yours”?

What is the best way to say this?

Because of yours and the John Wichel Foundation’s grant we are able to continue our mission to serve all Texans with diabetes.

Should it be

Because of your and John Wichel Foundation's grant, we are able . . . OR
Because of yours and the John Wichel Foundation's grant, we are able . . .

It's a double possessive with the word your. No matter how I write it, it doesn't sound right.

When using them separately, we'd use-

• Your grant...
• John Wichel Foundation's grant...

When using them together, combining them with an 'and'-

...your and John Wichel Foundation's grants...

... which, when placed into the context of this sentence, would be- "Because of your and the John Wichel Foundation’s grants, we are able to continue our mission to serve all Texans with diabetes."

Kapeezy's is the logical answer, but we don't always speak logically.

My sense is that yours and the John Wichel Foundation’s grant is not that uncommon.

I had a look at the iWeb corpus, searching for your[s] and someone else's.

I found that yours and someone else's had 108 hits, but I count around 36 of them before noun phrases (like "grant"), and the rest in contexts where you would expect yours on its one (eg Love a kid today - yours or someone else's.). Your or someone else's got 48 hits, all of them before NPs.

On the basis of that (one) corpus, then, your is more common in that context, but not overwhelmingly so. The GloWbE corpus gave me smaller numbers, but the same relationship: 6 your to 5 yours. On the other hand, the NOW corpus (News on the Web, so presumably mostly professionally written) has a much larger difference: 285 to 5.