Multiple options, it depends on what you want for a front sight. And if you want to remove the sight when using a scope so it’s not in the field of view of the scope. 

Lee Shaver offers Lyman style sights of various heights. Down side is they dove tail mount, so more or less permanent and will cloud vision through a scope.

CPA offers a dovetail mount that you can mount a Lyman 93 or similar sight that also has various heights. 
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Williams sight company Al Freeland both offer dove tail mounts that you can mount a dovetail sight in. 

Plenty of options

Way I handled it mounted my Lyman STS on the Pope stocked two barrel CPA. Various scope blocks raising the scope to a comfortable cheek position.

Then mounting the MVA tang sight raising it to match the scope’s comfortable cheek position, rifle rode same iron or scope.

Next put two zip ties on the two muzzles , CF & RF opposing. Wrapped the two together with fly tying thread, tape works too. Zeroed the rifle at 200 and gallery CF & 100 & gallery RF. Both with the rear set same height. Front sight height set by Cutting down the zipped front with wire cutters.  Same idea as fliing a muzzle loaders front down to zero open rear.

Measuring the 4 temporary fronts ordered blocks to run the detachable front globe sight proper height.

Ended up with the same offhand position any match that rifle shot. Admit the high front sights aren’t pretty, but true target rifles should be functional and consistent offhand position is essential. 

Boats

That’s what my sight blocks look like. Height each barrel is individually tailored to the bullets trajectory and stocks comb fit.

Picture worth a thousand words !

Boats