I've been using the MSR coffee gold filter basket for both coffee and tea for years and really like it. It sits in you mug suspended by the rim. Pour hot water over coffee grounds and let the whole thing sit for 4 minutes. Yes there is some sludge in the bottom of your mug, but let it settle a minute and there is no problem.

http://www.altrec.com/msr/mugmate-coffee-tea-filter