tripod advice: gh1 + sigma 400 + canon 2x

hi all-

hoping someone can recommend an affordable tripod that will suit my needs.  i need to mount my  gh1 + sigma 400 + canon 2x to it, in order to shoot birds that perch across the lake from me.  I have been utilizing the timer on my gh1 with the 3 shot burst option, and have noticed that the rather concussive gh1 shutter is shaking my slik u8000 tripod quite a bit, to the point that getting blur-free photos is beyond my ability.  i can see the effects of the shake in the quivering image on my lcd between shots, so i am fairly certain that a shaky setup is at least part of my problem.

so, can anyone recommend a sturdy, affordable (preferably $100 USD or less, used is ok) that can handle a fairly heavy setup and a slappy shutter?  many thanks for your advice in advance.