There's no rule about increasing only on a knit side. You can purl in the front and back of the first and last stitches.
Just purl as you would normally, but don't slide it off. Then put your needle into the back loop from left to right and purl again, then slide it off. It's a bit more awkward than kfb, but doable.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry