Cross-draw is a very good way to carry as long as you take into account a few things.
First, there is a grab issue. The cross-draw is easier for someone standing in front of you to grab the gun. (Of course, a strong-side can be just as easily grabbed from the rear).
Second, it is usually a little less concealable since it's not back on your waist where your arm naturally covers it.
Some cross-draw users develop the habit of carrying the off arm forward or with the thumb hooked in the belt to cover the gun.
The up sides are, it can be very fast since you can pull the coat open with the off hand as you draw the gun. With strong side carry you have to do both with the same hand.
The gun is easily accessible to either hand.
The gun is MUCH more accessible when seated, especially in a car.
The only reason the cross-draw lost popularity was because of the police grab issue. Prior to that most detectives and off-duty cops carried cross-draw.
Whether you need a safety strap or thumb break is personal preference.
A good holster that's closely molded to the gun or one with an adjustment tension screw really doesn't need it, but it does add a layer of security.
Most any holster made for a Colt Detective Special will fit, the only issue might be the slightly longer barrel.
One issue to consider is the very sharp front of the Magnum Carry muzzle.
My SF-VI was so sharp it cut up the holsters, until I rounded off the sharp edges slightly.
There are still a lot of cross-draw holsters made, so you'll have to do some searching.
Here's a link that has a list of the web sites of most of the holster makers.
http://www.coltforum.com/forums/showthread.php?t=28924&highlight=list+holster+makers