For my games I've ruled that it is the following:
Hoopak. Martial Weapon. 1d6 damage of either bludgeoning (staff/sling) or piercing (spear). The player can use it as either a sling, quarterstaff, or spear, switching which weapon they wield as a bonus action. It lacks the versatile trait or throwing traits from the staff or spear.
I then let kender treat it as a simple weapon as a racial, though I'd personally think it wouldn't be too big a buff to just give it to them as a racial proficiency using those stats Its a minor buff to a player at best tbh and is no worse than someone using a handcrossbow with proper feats.
The bonus action thing I took from a sword cane item that came from an npc in curse of strahd. Technically he's a monster, but the clear idea they had in the stat block was to take a short sword and let him change the damage type of the cane was sheathed. Same idea.