You can buy wooden beads from a craft shop, tie the figure-of-eight knot at the end, and then slip the bead onto it. But be sure the knot is big enough not to pull through, and if it isn't, you can tie a double granny knot just above it, which will eventually slip down against the figure of 8 (which won't slip, because it pulls in on itself).

Have to agree with you about tying the "proper" type of harp knot - I can never be bothered either and I've been playing for decades! The one I use is - I hope I'm getting the terminology right because this name was mentioned to me by a friend who plays harp and sails - a (?) Clove Hitch. I showed him my nifty harp knot and I think that's what he said it was. All I know is that it works and is much easier to tie, especially with temperamental & fragile gut, or irritatingly stiff Tynex/CF/nylon.

The two advantages of the Clove Hitch are that (a) you can tie them with one end of the string immobilised (i.e. already strung through the soundboard hole) because you only need to pass one end through the loop rather than needing to do both of them; and (b) they pull in tighter on themselves rather than slipping down. Sometimes, when the hole is hard to reach from the underside because it's too high on the harp to get your hand in, or it's behind a strut, you need to be able to put the string in from the top side of the soundboard and do the knot after it's already been passed through. (I use a wooden spring-clothespin to hold the string in place and make sure it doesn't fall out while I'm tying.)

I do put a toggle through the knot to anchor the string and stop its end pulling through - and I make these myself by buying a metre or so of electric flex (cord) and cutting it into little 3-quarter-inch lengths. (Use small wire cutters, not scissors cuz you'll wreck them. You'll want these to trim your metal-wound bass strings anyway.) The rubber coating on the flex grips the knot, won't cut through the string, and won't snare against the string bar. (Don't use bobby pins or safety pins etc for these last two reasons.)

So, high-tech gear harpies need to carry around for string-changing:

Wooden beads OR little pieces of electric flex (bell wire is too thin & can snap)
Spring-clothespin
Nail clippers to cut off the leftover string ends
Tweezers, in case the string is hard to catch ahold of to pull through the hole
Small wire cutters