My Maverick 88 is made that way. I emailed Mossberg asking for advice because I don't want to go the aftermarket route with things like slide tubes. I'd certainly like to be able to purchase matching furniture, so on the newer models with the molded action bars/forend, you need to purchase the correct length slide tube, a nut, and a forend nut tool. Here is what mossberg told me:
"Thank you for your e-mail. Yes, we do sell this action slide, item#11603BL action slide, price$34.00 and
Item#3408-1 action slide tube nut , price12.00 and we also offer the forend with ridges on the side. Item#10462 forearm price $18.00
Plus the shipping and handling $8.95 , You can order directly at
1-800-363-3555."