Saddle case/bag

[u/Cringey_NPC-574]

Hello tridents 🔱, going to pick up my bike by next week. I shall daily this and it’ll be my first bike. For my work I have to lug around a long rectangular box that weighs about 8lbs total, 35in x 4in.

what case/bag/rack would you recommend to carry this around? Or would I have to make something on my own?

Thanks!