You just have to get a 41 mag cylinder reamed to 45 Colt to get smaller throats, or a custom cyl but that's much more expensive.
Doing it yourself by finding a used cyl on Ebay and Gunbroker or the classified sections of the two Ruger forums is an easy way to go; timing will not be an issue. Just be sure to get a cyl with same overall length as yours or longer to fit your frame. And buying a reamer for about $100 or renting one for $40 is easy is a simple do it yourself because you'll be removing very little material from a cyl already bored to 41.
Here's a list of smiths with good reputations on the forum and some may have take off cyls:
Hamilton Bowen - Bowen Classic Arms
BCA Corporation 3512 Old Lowes Ferry Road
Louisville, TN 37777
Bowen Classic Arms Corp.
P. O. Box 67
Louisville, TN 37777
David Clements - Clements Custom Guns
2766 Mt. Zion Rd.
Woodlawn, VA 24381 email@example.com Clements Custom Guns
Cylinder and Slide
245 E. 4th Street
Fremont, NE 68025
Phone: (402) 721-4277
Fax: (402) 721-0263
Orders Only: (800) 448-1713 Home
Ben Forkin - Forkin Custom Classics
PO Box 444, 205 10th Ave SW
White Sulphur Springs, MT 59645
John Gallagher - Gallagher Firearms Inc.
3923 Bird Farm Road
Jasper, Alabama 35503 firstname.lastname@example.org
closed website: www.gallagherfirearms.com
Alan Harton (Colt SAAs also)
713-772-8314 or 713-907-6031 email@example.com
Sharpstown, Texas, West S/W of Houston
Makes a .327 Fed Mag Bearcat; Custom Ruger New Bearcat from Single Action Service Chambered for the 327 Federal Magnum Cartridge
Andy Horvath - DIAGONAL ROAD GUN SHOP
14131 Diagonal Rd.
La Grange, OH 44050
(440) 458-4369, (440) 355-5618
Jack Huntington (may start barrel re-boring)
JRH Advanced Gunsmithing
385 Freeport Blvd, Suite 13
Sparks, NV 89431
New website: JRH Advanced Gunsmithing
old site: Jack Huntington - Accredited Gunsmith
His turnaround time is short, his work is first rate, and his prices are reasonable.
Dustin Linebaugh - Dustin Linebaugh Custom Conversions
PO Box 263
Cody WY 82414
mailto:firstname.lastname@example.org Dustin Linebaugh Custom Conversions
John Linebaugh - Linebaugh Custom Sixguns
P.O. Box 455
Cody, WY 82414
177 Louis L'Amour Lane
Powell, WY 82435 Welcome to John Linebaugh's Custom Sixguns -
Amarillo, TX COWBOY ACTION FIREARMS - LONG HUNTER SHOOTING SUPPLY
Sounds like a nice package for $135.
Taper cylinder and ejector rod housing $45.00 USD COWBOY ACTION FIREARMS - LONG HUNTER SHOOTING SUPPLY
Garry Reeder - Garry Reeder Custom Guns
The Pistol Parlor
2601 E. 7th Ave.
928-527-4100 / 928-526-3313
mailto:email@example.com Gary Reeder Custom Gun - for 30 years a leader in custom handguns and rifles.
Ryan Ross www.ryanrossrestorations.com
8752 Turtle Road
Whittemore Michigan 48770
Turnbull Manufacturing Co.
6680 State Route 5 and 20
Bloomfield, NY 14469
Visit our shop
Mon - Fri 8:00 AM to 4:30 PM firstname.lastname@example.org Turnbull Restoration & Manufacturing Co.
Vans Custom Guns
NIGHTOWLS 1996, Utah NightOwl's Gunsmithing - UTAH's Best Gun Smithing Service