Well, first of all you could always use the connector that was on your old too short hose to hook up to the new hose.
Second choice is that you get a Thetford connector at a decent RV store (Camping World may or may not be decent - I make no representations - but they do have them in stock here). The Thetford connectors are usually WHITE as opposed to the other stuff that's black or blue...
Third choice is that you can order Valterra Universal Adaptor T05-2285VP "Converts Thetford System to Standard Waste Caps and Hose Adaptors".
I also bought a "Sewer Solution" and for that you'll need the "Universal Adaptor". Camping World did not have these in stock, and I ordered three of them from some RV parts outlet back east - do a search here and you'll find it.
"Between what matters and what seems to matter, how should the world we know judge wisely?" - E.C. Bentley, Trent's Last Case