Well, if your Permacomb arrives usw it.
Else you are member of a beeclub? If yes call them, i bet someone will have foundation laying around and is willing to sell it. But go for foundation, not drawn, so you won't import any diseases.
If not, buy some beeswax. Take a wedge about 3/8" high, half frame with - 1/25" thick, water it, insert into the frame, against the top bar and pour wax onto it. Thus getting a starter strip cast onto your top bar.
Most times, just pouring a small line of beeswax onto the top bar, is enough, but the edge created with the wedge method, makes it way more safe. But remeber with only starter strips, you hives neues to be level, else the end of the comb will be outside of the frame.