I wouldn't bother. I cannot imagine you feeding the worms enough citrus to significantly change the pH. Earthworms castings are pH neutral.

If you have eggshells, grind them up and toss them in. The worms appreciate the calcium.

Are you juicing?

I would add tons more dry corrigated cardboard or other bedding such as dry leaves dry newspaper or what is free in your area.

How do you know your bin is too acidic?

Add any egg shells you have. I would be tempted to make little half egg shell citrus bombs. Fill each egg shell with pulp and toss into bin. Any acid would eat away the shell. It would be fun to see if that happens and how long it takes for the eggs to become worm love shacks. If that happens it was not too acidic no matter what any test says. I would also leave the cover off so orange smell does not chase away worms.

personally would not buy anything to manage ph in a worm bin. if you have any of these items on hand then it can't hurt i guess. better method ... put the citrus into a backyard composter and feed them the partially composted material. or put them in an open containter, let them rot/dry a bit and feed them to your worms. the citric acid will be broken down over time by bacteria and then should not be a problem in a worm bin. otherwise mix the citrus with enough innocuous material (half citrus half shredded cardboard?) and it should likely be ok.

on the other hand; eggshells, oyster shells, bone meal, gypsum, wood ashes are good material to have in your compost. if you are using the compost for your garden then these items are good things. be careful with the wood ash though, it's quite alkaline but a good source of phosphorous.