Curious if the highlighted part may have a universal fit option that a Lowes or Home Depot would carry. Its the seal on the bottom of the supply line of a Delta Faucet. It sits right below the nut so when you instal the pex line into the 1/4 turn valve it will seal the pex to the valve to prevent water leaking. Once seated the nut will secure it.

Would this be an item I can find in Houston right now or a universal option?

I had a similar issue . And was able to find the same part . Do you have a picture of it? This was the gasket mine had .

You can order it online,
You may have luck at a plumbing supply.