Marcus there are some things you need to be aware of. First the bandwidth of a small magnetic loop, like your describing is really small (2-6 KHz) for the frequency range that your describing. Assuming that is ok I don't know of a commercial solution. You can use this calculator to get a general idea
http://www.66pacific.com/calculators/small_tx_loop_calc.aspx .I am currently planning on building one of these loops for the 40-20 meter bands using heliax 1 5/8 inch for the outer loop and a vacuum variable for the tuning capacitor controlled by either a arduino or rasp pi. I am still working on my plans but if your intent on utilizing one of these antennas I suggest you check out the group at
www.magloop.com. If you not planning on transmitting a PA0RDT may be better. It is smaller. It is an active antenna and does require power but the websdr guys are getting good results with it. I would like to build one in the future as well. See google for more references but it is suppose to work well from 10KHz to 30MHz.