Hi, You say you are looking for a battery powered tester, check out the Seaward Primetest and the Martindale HandyPAT ranges also. I can recommend the Seaward Primetest 350 and Martindale Handy PAT HPAT600 in particular.
Be aware:- Although having a battery power PAT tester appears to be a plus point and attractive feature, it does have a big minus point, one that can seriously effect you potential income, notably the inability to do run tests. Most industrial and commercial contracts I see frequently specify equipment run tests, particularly those from the MOD, NHS, Local Authorities, Schools, Colleges and Universities.