Consider buying a bobbin winder. These are more typically used for weaving but they are a boon for the hand spinner. First, if you have an antique wheel (I have a CPW), it probably came with only one bobbin*. It costs around fifty dollars to get a new bobbin made and while it is being made, you'll be without your wheel because the wood turner will probably need the flyer assembly to make a bobbin that actually fits. Using a bobbin winder and weaving spools or bobbins for storage allows me to spin as many singles as I need for plying on the CPW. Even a modern spinning wheel bobbin can be pricey; the Aura's are about fifty dollars
Another reason to invest in a bobbin winder is the improvement in plied yarns rewound bobbins afford. There are folks who have been spinning way longer than I and who know way more about spinning than I ever will. They recommend winding off to storage bobbins and plying from those. The action of winding off leaves you with a neat and tightly wound bobbin from which to ply and gives you a chance to even out the twist in a single.

Cost? I got my winder from Fiber Artists' Supply for about $65.00. The bobbins are Leclerc styrene spools from Webs....they are about four dollars. So, for about the same cost as a new bobbin for my CPW, I have a winder and a bunch of spools and I make a better yarn. Seems like a bargain to me.
*My CPW probably had only one bobbin when it was new. On the flyer arms, there are visible grooves where yarn rubbed the wood as it was wound yarn directly off the bobbin. I recall reading somewhere that the bobbin was rarely removed from these wheels.
They are assembled. Each has its own strengths and each may have a weakness, although you'd have to ask me very, very nicely to get me to admit any of them have any weakness of any sort whatsoever. And of course, the weakness may well be mine and not the wheels.

They are (in no particular order) a cherry Schacht Reeves (30 inch), a Cadorette CPW, a Majacraft Aura and a Roadbug from Merlin Tree. It has taken more than two years to get them all into my house and my hands. It wasn't hard but it required more patience than I'm used to exerting and a lot of help from a special Aunt and a special friend. My Aunt is amused at the way I spin because I usually have all four wheels at work all the time. The Roadbug is always ready for travel and the other three stay home.
Are there other wheels in my future? I only need a little bit more room.