The shirt is by designer Jeff Banks, and can be found on the Debenhams website, currently at a discount.
Sadly it doesn’t have the tabbed collar, but it does tick a lot of other boxes, so that can be forgiven.
The thing that makes the shirt worth a look is the fabric it is made from.
There was a neat close up of the shirt in Closing Time, when The Doctor points out his here to help badge (see below).
The shirt’s fabric has a very distinctive grid pattern to the weave, which can only be seen in this tight shot.
The Jeff Banks shirt is a very similar fabric weave - and just the right colour too! (the screencap above is very heavily altered in post-production, so not necessarily a good guide for colour)
Personally, I think it’s the best one I’ve seen so far, and highly recommended.