There's a few ways you can go with this
Check YouTube for gommies bullpup,he used a Ripclip on his
If you have some fabrication skill you could build a boxmag,deallen did a nice one here,search G1 pistol.I've done 4 different boxmags with Ions,use an RF board to gun interfaced hopper if you do.
If you want to run limited paint and not spend much $ you could make your own longbow setup pretty easily,used one's aren't cheap or easy to come by
I also made a full custom First Strike magfed bullpup using mostly SP1 parts.It took me a few years to do as I changed it several times while building.By scrounging metal,parts,and plastic it cost around $500 to build,about the same price as a production magfed though mine has eyes and will shoot 20 bps
Needless to say the SP1 is easy and cheap to mod,for less than the cost of a DAM you could build a boxmag,longbow and First Strike gun AND it will crono
Here's my Photobucket to give you a few ideas