Suggestions on a 3-pole manual transfer switch

Installing a Victron Multiplus II inverter but keeping my Magnum as a back up. Looking for an appropriate 3 pole 50 amp transfer switch so that I go from L1, L2 and the neutral for the Magnum to the house as it is now, or power L1 and L2 to the house with the Victron.

L1 and L2 would only be tied together in the transfer switch and ONLY when selecting the Victron inverter. 

 I will be using it to go between the Victron (my main one) to the Magnum (backup). The Magnum is 240 and the Multiplus is 120. I plan on tying L1 and L2 together for the Victron in the transfer switch. I have nothing in the home that is 240, no 240 volt circuit breakers and a fairly balanced load of 25 amps and 19 amps on L1 and L2, with ABSOLUTELY EVERYTHING on in the house. MOST of the time the load is 9 to 15 amps AC. I also have no shared neutrals.

I do not run a generator at the present time. 

Looking at several different switches, including this one from Midnite Solar, MNTRANSFER-60A. Also this one on Amazon. Amazon.com: MUJURUR 100A Generator Transfer Switch, 24000W Heavy Duty Double Throw Safety Switch, 120/240V Manual Transfer Switch, Stronger Stability, Enlarged NEMA 3R Enclosure for Outdoor, 10-Year Warranty : Patio, Lawn & Garden

Any suggestions or recommendations?