Turn signal

I understand the turn signal parts/guts are available for a 65 Valiant, but expensive.

Depends how we define "expensive". See here. Remove/replace switch is about a 30-minute job if you haven't ever done it before.

My question is what other options exist to get them working?

1. Get a used switch that's probably roughly just about as worn out as the used switch you already have.

2. Find a slightly cheaper price (or not!) on a poor-quality turn signal switch-shaped trinket from China that won't fit right, and will break early and often.

3. Leave wires dangling under your dashboard and label them with little flags of masking tape, then reach down and twist the correct wires together whenever you want to operate a right or left turn signal.

4. Forget it all—roll the window down and use hand signals that nobody has understood since about 1953.

is there a way to retrofit newer parts or a suitable replacement steering column we can use?

For less money and effort than just repairing it correctly? No.

We want to convert it to floor shift eventually so replacing the column doesn't bother me a bit.

One kind of switch fits '62-'69, so even if you swap in a column without a gearshift built in…you're still lookin' at the same switch.