There are many good mics used for other drums that are on the market. You might consider making trips to several local music stores (where they sell drums) and speaking to the sales guys. You'll learn some good tips from the good ones, about what mics might be good choices. In our band, Eammon uses a Senhauser 835S, on a stand. As Rich said above, with a mic on the stand, you have the ability to move away or onto the mic, thereby increasing your dynamic range. BY the way, you may find the fault is not so much the mic as the rest of the acoustic environment; ie the EQ capabilities of the mixer, the 'strength' of the signal (the input gain), mic placement, proximity to speakers (house and/or monitors) etc. I find that all of these things conspire to reproduce good bodhran sound (or not).

One tip you may find worth investigating with the mic you have; be sure that you are getting the optimum input gain setting for your bodhran. This will give you the best dynamic range, and the strongest clean> signal possible for EQ at the mixer. Many mixers have an LED dedicated for optimizing the input gain. Be sure you play your ablsolute loudest when setting it up. Once set, you will be able to adjust the tone controls to get the best EQ. If you move the tone much, be sure to recheck your input gain. You'd be surprised how much quality you can gain by refining these settings.