The 357 (ENERGIZER 357/303H) is a silver oxide battery with a relatively constant voltage during its life until the voltage drops off sharply when it dies. A standard replacement is SR44. The 357A is an alkaline battery the voltage of which drops slowly and constantly during its life. There are also silver oxide versions of this cell (ENERGIZER 357/303) with similar voltage characteristics. A standard replacement is the LR44. Practically, if your device is more demanding of its battery (for example, fancy calculators and measuring devices), use the 357, if it is less demending, you can use the 357A. If you try a 357A, and your device doesn't run very long on it, then it is more demanding, and you should switch to the 357 next time you get new batteries.
Remove the #8 x 1/2" screw from the back of the monitor. Remove the two screws from the back cover of the monitor and remove the back cover. Push the two old batteries out of the clips and insert two new batteries. Batteries are L1154 watch batteries. Adjust the air gap between the left pedal frame magnet and reed switch until there is a 1/8 inch gap. Retighten the screw on the reed switch after adjusting the air gap.
I got a magazine for a Model 23A from bob's and he advertises magazines for 23Bs. 23Cs and 23Ds.Bob's Gun ShopPo Box 200 Royal AR 71968Phone 9 to 4 Central Time (501) 767-1970 WeekdaysGo to:http://www.gun-parts.com/index.html/Then select Savage/Stevens Rifles from the list. Half way down the page you will see this:SAVAGE STEVENS MAGAZINESSavage/ Stevens/ SpringfieldClick to Enlarge Picture#1 Standard 22 LR 5 Shot.....................$25#2 Standard 22 LR 10 shot...................$30#3 Any Model Canadian Below.Canadian Backordered until AprilStev 62 Canadian.10 Rd...Net.22 Lr.....$30Stev 64 Canadian..10 Rd...Net..22 Lr...$30Stev 954 Canadian.10 Rd..Net.22 Lr....$30#4 1903,1906,1909..8 Rd...22 Lr...........$35#5 Savage 19.NRA..............7 Rd..22....$35#6 1922 .22 LR.......5 Round...............Out#7 Savage .22 MAGNUM...4 Rd.........$357A Magnum not shown 8 Round..........$45#8 Model 23A .22 LR Not shown.........$35#9 Model 23B .............5 Rd....25/20....$35#10 Model 23C.............5 Rd....32/20....$35#11 Model 23D.......5 Rd...22 Hornet...$35Order per their instructions.