As most have said, just about any heater will work. A few things to consider:
Type: Don't get hung up on "ceramic" or anything else. 1500w is 1500w. The differences in fans can make a small difference, but the Rpod is so small that you're unlikely to notice it.
Noise: Smaller heaters use small fans operating at higher speeds. This translates to more noise.
Thermostat: Many heaters have thermostats that aren't very good. One major problem is that the thermostat is too close to the heat source. I personally have yet to find one that is repeatable.
I'm considering buying this:
http://www.amazon.com/gp/product/B000E7NYY8/ref=s9_simh_gw_p60_d7_i1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-3&pf_rd_r=1THRZAJ4S7CD5AAXSED9&pf_rd_t=101&pf_rd_p=470938811&pf_rd_i=507846
You can plug any old heater into it and have a good thermostat that is farther away from the heat source. I haven't used it yet, but it seems ideal for the need.