This could be what youre looking for, small, cheap and available in 27 and 40 mhz
Cirrus 4 Channel 40MHz FM Receiver-
Okay not Futaba but this Cirrus 4 channel 40MHz FM receiver is compatible. It's super small, lightweight and low cost narrow band that is ideal for cars, boats and robots. Use only Cirrus or Futaba single conversion 40MHz FM crystals. Size 37.5x22x12.8, weight 6.5g
Try DMS-Racing for one 