Serious solderer? Got one of those 0.7mm 0.5kg reels? Don't want to lug it around when soldering out in the field? Eat some Tic Tacs and print these 4 small parts and you've got yourself a miniature solder dispenser that holds about 24 grams worth.
I printed mine in PLA at 0.10mm layer height with a Prusa i3 Mk3, no support needed, one of the halves of the reel has a 1.2mm hole in it to poke the solder into to grip it when spooling it up.
Once the parts are clipped together, remove the top of the Tic Tac box - cut or peel off the sticker then open the tab, insert a small screwdriver and lever it off - then poke a small hole in the lid from the inside with some tweesers or something but not too big, you want it to grip the solder a little, fill up the little reel from your big reel then insert the wire through the hole in the lid, put the printed holder in the lid first and then into the main part and shut it tight.
Removing the lid afterwards without damaging anything is easy, open the tab, insert small screwdriver between the top of the lid and the printed parts and lever it open.
UPDATE: This version is for the 16g Tic Tac boxes, I've remixed this for the jumbo 49g Tic Tac boxes - https://www.thingiverse.com/thing:3344104
And also for the American 29g Tic Tac boxes - https://www.thingiverse.com/thing:3354779
UPDATE 2: I have designed a holder for this size Tic Tac box, with the side specifically cut out to match the size & position of the solder reel inside the box.
It fits near perfectly when printed on my Prusa i3 Mk3, 0.2mm height, 20% infill, and the box doesn't move or fall out when in the holder.
There are 3 variants, 'wide' for a sturdy base to help stop it being knocked over when in use, 'narrow' so it can be attached to a surface, both of which have 2 mount holes 20mm apart for M2 bolts with 2mm high heads.
The 3rd variant is a very simple design for remixing however you want - I attached 8 in a row to hold 8 reels of different coloured wire wrapping wire in Tic Tac boxes.
UPDATE 3: I designed a small part that will hold the spool in a cordless drill so you can fill up the reel in seconds rather than minutes.
It needs to be printed either at 100% infill, or at least 4 perimeters for strength, 0.2mm height is fine.
Clip the two halves of the spool together, put the winder part through it, press it into the drill as you tighten the chuck, put the solder in the hole in the hub and wind it round a few times manually, then spin the drill, but not too fast, just a little is enough.