We've searched the internet and found the largest collection of On30 Scale trains for sale is on eBay. Below are the listings for 'baggage car'.

SANTAS LITTLE HELPERS BAGGAGE CAR 2009 HAWTHORNE MM HOLIDAY EXPRESS NIB
SANTAS LITTLE HELPERS BAGGAGE CAR 2009 HAWTHORNE MM HOLIDAY EXPRESS NIB
$74.99
Time Remaining: 8d 21h 33m
Buy It Now for only: $74.99
On3 On30 WISEMAN MODEL SERVICES SM 105 DRGW RPO BAGGAGE PASSENGER CAR KIT
On3 On30 WISEMAN MODEL SERVICES SM 105 DRGW RPO BAGGAGE PASSENGER CAR KIT
$99.95
Time Remaining: 11d 2h 14m
Buy It Now for only: $99.95
Coca Cola Hawthorne Village Baggage Car
Coca Cola Hawthorne Village Baggage Car
$99.00
Time Remaining: 15d 4h 40m
Buy It Now for only: $99.00
On3 On30 WISEMAN SM 101 DRGW OPEN PLATFORM BAGGAGE PASSENGER CAR KIT
On3 On30 WISEMAN SM 101 DRGW OPEN PLATFORM BAGGAGE PASSENGER CAR KIT
$89.95
Time Remaining: 25d 10h 35m
Buy It Now for only: $89.95

Other On30 Scale train items recently purchased through this site:

SANTAS LITTLE HELPERS BAGGAGE CAR 2009 HAWTHORNE MM HOLIDAY EXPRESS NIB
On3 On30 WISEMAN MODEL SERVICES SM 105 DRGW RPO BAGGAGE PASSENGER CAR KIT
Coca Cola Hawthorne Village Baggage Car
On3 On30 WISEMAN SM 101 DRGW OPEN PLATFORM BAGGAGE PASSENGER CAR KIT