There was only a short period in late 1968 and early in the 1969 GP seasons when they used two wings. Most commonly seen with two wings is the Lotus 49B (as the orange car in the photo above) The GREAT news is that there is an old Heller 1/24 Lotus 49B kit, although it is from later in the season and only carries the tall wing aft, not forward. This kit shows up on eBay pretty frequently, either in a Heller box or a Union box. Same kit. Both Heller and Union's kit decals are for the red, white and gold colors of Gold Leaf Team Lotus.
As Jack says above, it should be pretty straightforward to scratchbuild that forward wing.
The other "biplanes" in Formula 1 were Matra and Brabham, in versions not produced in kit form. Heller made a Brabham BT33, a few years newer than the biplane period, and a McLaren M7, which has the tall rear wing. I believe the McLaren M7 never ran with two wings.
The biplane wings were also run on a few Formula 2 cars, but I haven't seen any of them in kits.
Good luck,
Rick