There is no such thing as any GMO plant that the general public can buy.

None.

Let me say that again, there are no GMO food plants you can buy. Anyone that makes a point of saying their line is GMO free is basically scamming you to try and make some extra money by scaring you with straw men.

Concur. The major virus for squash is Mosaic virus. While there are squash that will tolerate it, none are resistant. It does not fit your description. I expect that you have an insect problem, probably cucumber beetles which vector bacterial wilt. Get your Ag extension agent to identify the problem and the look for appropriate varieties. You can probably find an OP that meets your needs. Hybrids are better at production and resistance to some dreaded diseases like mildew. GMO's are the modern boogey man, but none are available to home gardeners.

"GMO's are the modern boogey man"

And are about as dangerous, but that's a different thread.