you can buy the 2 halves from mossberg. left and right flat top stock #19564 and #19565 ,left and right fore arm #19566 and #19567. each flat top shell half is $12 and forearm$7.25. less than $30 for 4 pieces.
# 19570 TACTICAL STOCK $30.00
# 19564 RIGHT FLATTOP SHELL $12.00
# 19565 LEFT FLATTOP SHELL $12.00
# 19566 RIGHT FOREARM $7.25
# 19567 LEFT FOREARM $7.25
# 19250 RIGHT RELEASE LEVER $3.25
# 19251 LEFT RELEASE LEVER $3.25
# 18462 PLASTITE SCREW#2 $2.50
# 19255 PLASTITE SCREW #4 (need 18) $2.50 each x 18 = $45.00
# 20011 REAR SIGHT ASSEMBLY $29.99
# 20012 FRONT SIGHT ASSEMBLY $20.00
# 19249 BARREL BAND SLING SWIVEL $3.50
# 19568 ACCESSORY RAIL (need 2) $3.25 each x 2 = $6.50
Flat Rate Shipping - $10.95