Larger traps, such as a racoon trap, (36x12x14) with doors on each end, are beneficial because they can double as a holding cage for a few days before and after surgery.  A, "trap isolator or divider",  is needed so that the cat can be contained to one end of the trap while cleaning and refreshing food and water daily. 

See: How to Perform a Mass Trapping video from Neighborhood cats.

http://www.neighborhoodcats.org/ 212 662-5761

Safegaurd Large Racoon Trap with Rear Door, Model SG-36D

From Animal Care Eqiupment and Services ( ACES) 10% discount when ordering two or more.

1 800 338-2237   http://www.animal-care.com/traps.aspx ( Traps and Equipment )

TRAP ISOLATOR Model TD-2

From Animal Care Eqiupment and Service 1 800 338-2237

http://www.animal-care.com/product_list.cfm?sub2a=28&prod=1 ( Traps and Equipment )

TRU-CATCH TRAPS

*Model 36D with rear door 36x12x14 oversized doubles as a holding cage

Model 30D with rear door 30x9x11

Tru - Trap Divider

TD-2 for #30 and #36 traps

www.animal-traps.com ( Tru-catch traps )

TOMAHAWK TRAP Model #107 with rear door 32x10x12

http://www.livetrap.com/cgi/search.cgi?user_id=27947&database=dbase1.exm&template=template1.shtml&0_option=1&0=107 1 800 272 -8727

HAVAHART TRAP # 10791. http://www.havahart.com/store/product.asp?dept%5Fid=46&pf%5Fid=1079&mscssid=J9EUD396FPDE8G0D40PEE6SKA608BJT1 1 800 800 1819

Home Depot and Agway Garden Centers on LI carries.