Replacing tongue and groove floorboards: but can’t find a match

A room in an old farmhouse, formerly a porch, now enclosed, has floors made of tongue and groove lumber. I need to repair those floors by replacing at least some sections of floorboards – somewhere between 10-30 linear feet.

Each original floorboard has a 3 1/4 inch face, and is 3/4 inch thick. I'd guess it was milled from 1x4s, removing 1/4 inch sections to make the tongue and groove. Tongue and groove each have 1/4 inch measurements.

All the off-the-shelf replacements I've found have a 3 1/8 inch face, and are something less than 3/4 inch thick. Close but no cigar.

If I use the off-the-shelf replacements, that's going to leave a big gap, and I'd rather not. Since I can't find off-the-shelf materials that match the original measurements, maybe I should try to fabricate replacements myself?

I have a table saw without dado, and I have a never-used router and small router table. I think I could take 1x4s and slice out the material on either side of the tongue on the table saw and make the groove with two passes; or I could try to use the router, which I have no experience with. Whatever I did would at best result in square sections, not the rounded sections in the original material. (See photo below.)

So, three questions:

1. Are off-the-shelf replacements for these available and I just don't know where to look? Ideas?
2. Will square sections instead of rounded ones be adequate?
3. Table saw or router?