The style of short formal jacket which can be substituted for a PC is called a "Spencer Jacket":

SPENCER JACKET

A style of tuxedo jacket whose hem is just below the waist, rather than below the hip. At the front opening, the hem dips into points, so that the Spencer resembles a tailcoat without the tails.
Another site gives the Spencer's origins:


Earl Spencer and the Short Spencer Jacket 1795

The Spencer was a short top coat without tails worn by men during the 1790s as an extra covering over the tailed coat. It had long sleeves and was frequently decorated with military frogging. Its originator is thought to be Earl Spencer who singed the tails of his coat when standing beside a fire. He then had the tails trimmed off and started a fashion.
I agree with Brian; I personally would stear clear of the "Western" style jacket. The Spencer is similar to the "mess dress" jackets for the British Army.

Cheers,

Todd