Seat pack would have to be small otherwise it's going to get hit by the rear wheel with the dropper down. I think weecog do a tiny one. For tools and a mini pump only I use a waist pack but this doesn't give me anywhere to store water for longer rides.
Maybe a top tube feed bag would be good for tools but it would only have room for CO2 cartridge and not a pump - you could then get a waist pack for a water bottle.
Not sure if you're looking for a custom frame bag but www.bike-bag.co.uk made a bag for my DIY ebike for £67.50 - i'd recommend him if budget and custom is at the top of your list. He can also do custom embroidery on the bags too.