Stock guides work just fine, they are trimmed down on the nose ( the part that is in the port ) this is to reduce the guide side loading from the long side of the port and going in slightly crooked... as it's installed. This is normal practice for ports that have more material on one side than the other supporting the guide.
Having said that, you should core drill and remove your damaged guide and measure the bore to determine the OD size of guide you need, perhaps you will need a slightly oversize guide to get the right press fit...
Hope this makes sense.
Cheers