Yes, many. Do a search in this form for "synth" and you will find pages and pages of info about them.
Your options are standalone pedals, multieffects with synths, or individual pedals that combine together for a synth effect.
Cheap standalones are the Boss SYB5, Behringer BSY600 and Ibanez SB7.
More expensive are the ElectroHarmonix Bass Micro Synth, Markbass Super Synth, Chunk Systems Octavius Squeezer, Akai Deep Impact (discontinued but available second hand for lots of money), Korg G5.
For multieffects, check out the Zoom B3 or MS60B, the Line 6 M5/9/13 or the Boss GT 10B or ME 50B.
For separate effects, try a fuzz into octaver into envelope filter into chorus. A gated fuzz like the Wooly Mammoth or Iron Ether Oxide will give you a hard on off envelope.
A final option is the Roland GR-55 or VB
-99 which model various synth sounds using a special pickup