You could match your iron shafts, or, your hybrid shafts (if you carry one). But, it is not a good idea to take a recommendation from some one who knows nothing about you or your swing

We have no idea what shaft which will work best for you.
The shaft size is a .335 taper fit - standard for Titleist irons. “The world is your oyster” for options. Your current irons would be a starting point.

I believe the 712u would use a .355 taper tip but I would double check with customer service. I don't think Titleist would send just a shaft but you may be able to send it to them.

If not, perhaps check this shaft out.

www.golfworks.com/.../

Having reshafted a MP-20 HMP to graphite twice, I can say you need to make sure you take it to a club fitter that knows what their doing.

I initially took it to a big box store and they didn't weight it properly. I needed to add 10 grams of lead tape on the back to get it up to D3. I had it fixed and the builder put a 10g weight in the shaft tip.
This shaft was a Project X Evenflow White 6.5 at 95g. It was 1/2 inch longer than standard...also a mess up by the big box builder.

That shaft broke and I got a LAGP Tour AXS 105H-X 110g shaft. This was cut to standard. The build needed the 10g weight plus 10 grams more lead tape to get it to D3.

The original shaft was a True Temper DG AMT Tour White S300. the 3 iron shaft was 112g I believe.

True Temper has acquired Steel Fiber which makes a graphite shaft very similar to Dynamic Gold. I would write to True Temper and ask them.