Which "Bobby tone"? I've been listening to some early 70's lately ('70 - '71) and Bobby has that warm, clean 335 tone (or whatever guitar it is - maybe an SG) and Jerry has the fat Gibson tone. Dig it.
I love the late 70's to mid 80's flanger Bobby tone too. I stopped liking his tone from '85 on. Just sounded like crap to me. More distorted and just bad tone.
Maxon PH-350 would be my - "you have to sound like Bobby but can only bring 1 pedal and a tuner" choice.
There are some flanger pedals that could work nicely but I've got no experience in flanger pedals....
Another pedal option would be an EQ and guitar mod. Get yourself a toggle to toss your pickups out of phase. It sounds filtered and quieter so you'll need something to boost your signal and maybe a low-mids boost too.
Stopped by my local music store and played around with an ibanez cf-7 today. It has a has a Krazy switch for some vibrato-like chorus and flange too. Sounded OK but pretty hissy and doesn't seem like it could take a stomp.