I allow after-market modifications for weapons, shields, and armor.
But what if 1d weeks to wait is too long? ("But I'm mad now!")
A rush job - turning 1d weeks into 1d days - is as-written but costs 5x as much. This is cumulative with the cost modifier for a rush job.
It should really cost 7x as much (it's 7x faster!) but 5x is easier math.
What if you absolutely need it by tomorrow? 20x as much.
This roughly based on the "average" 3.5 days wait, so 5 x 3.5, rounded up to the nearest easy number to remember.
Using the same example as last time:
For example, silver-coating an $80 morningstar will cost $160 (+2 CF) as original manufacture, but $320 (+2 CF, x2) done to an existing weapon. Getting it done in 1d days instead of 1d weeks costs $320 (after-market) x 5 (rush job) = $1600. If you need it done in a day, the smith will drop everything and do it for $320 (after-market) x 20 (immediate work) = $6400.