you "could" try 2 x stick or thin block batteries in parallel ???
2 x 1500mah 25c - cut and join 2 positives together then join 2 negatives together
3000mah 25c battery - still 25c you don't get a 50c burst - its still 25c but bigger capacity
This is not as perfect as a dedicated 3000mah lipo but if range/size options is a problem
then it is a possible consideration as you might source a battery for each crane/nunchuk "tube"
then link up 2 x 1000mah or 1300mah to make a better lasting capacity perhaps
(same battery types work best obviously if possible)
reckon this could be a starting point:
http://www.hobbyking.co.uk/hobbyking/store/uh_viewItem.asp?idProduct=44772
now one twin stick could fit down one tube.....
so you could fit these down each tube
= 2 x 1200 = 2400mah 25c if linked in parallel
or just fit two batteries in stock and might be able to quickly swap over from one 1200 to other when gun slows down
should last you the morning - lunchtime replace - rinse and repeat etc......
but reckon if that battery don't fit in there then get another stock