So are you talking about a one string fiddle? That’s weird, Home Depot in my area carries steel wire? have you tried Ace Hardware, they carry steel wire?
It depends how much tension you want. I calculate that a plain steel 0.064 (the middle of your range) would be 40lbs of tension when tuned to D3. That seems pretty high to me.
If you look at 4/4 sized violins (13" scale length) they usually have string tensions of 12 to 18lbs. If you wanted to go for a tension in the middle that range... use a plain steel 0.040 for 15lbs of tension when tuned to D3 on a 14" scale.
A violin string is always the best choice, but this what I used? Actually piano wire, so better than construction wire? I’m in Cali, so it may not be available in your area? https://www.homedepot.com/p/OOK-9-ft-50-lbs-Smooth-High-Carbon-Stee...
I think that’s a Toombi not a Rawanatha?