@snottyotter's suggestion is a good one - for what you'd pay a bike shop to fix it you can easily buy a pack of nipples (NB you'll need to match the length) and a spoke wrench and do it yourself.
it's as simple as remove tyre, tube and rim tape; bit of grease on the spoke threads and inset through rim into nipple then tension.
without a tensionmeter you won't know the exact ideal tensions in the wheel but by sound and the trueness of the wheel you'll get close.
if it, or another nipple snaps at the shoulder you've got a problem with the build and i'd take it to a wheel builder to sort out.
@snottyotter's suggestion is a good one - for what you'd pay a bike shop to fix it you can easily buy a pack of nipples (NB you'll need to match the length) and a spoke wrench and do it yourself.
it's as simple as remove tyre, tube and rim tape; bit of grease on the spoke threads and inset through rim into nipple then tension.
without a tensionmeter you won't know the exact ideal tensions in the wheel but by sound and the trueness of the wheel you'll get close.
if it, or another nipple snaps at the shoulder you've got a problem with the build and i'd take it to a wheel builder to sort out.