I know you don't want to hear this, but a tension meter isn't the right tool, nor is it necessary.

Start by replacing the spoke, and aligning the wheel by degrees. Be sure to add spread the corrections among several spokes rather than overwork one or two.

Once it's reasonably true, spin the wheel pinging spokes with your thumb nail, listening for spokes that sound highest and lowest, and tweak the tensions accordingly.

Note, that badly untrue wheels rarely come back to true with even tension. Uneven tension is needed to force the rim true against it's warped condition.

All that said, I have a NOS unused Wheelsmith tensiometer, new in original box, and can sell it for $80.00 Inc postage within the USA.