Hello Tore,
no, Reynolds does not list any suitable tube for such cases.
But have look in the thread Suppliers for straight gauge thin walled tubing in Europe? and find some small diameter tubes. Attention: Aircraftspruce Europe does not display the actual prices for the tubes, they’ll add import taxes.
If not, maybe you might change your design to a single top tube with additional stays? Yes, that’s a different look, I know …
And don’t hesitate to ask Reynolds for infos about their tubes.
Johannes