Hi @robrm,
Here’s a link to the ifixit [guide|62597] guide.
There is also this [guide|56082] guide just to make you aware that there may be a difference in how the battery is connected to the systemboard in the tablet.
In the earlier version of the tablet, as shown in the top guide, the battery connection is soldered onto the systemboard, whereas in the later version, as shown in the next guide, it is plugged into a connector.
Replacement batteries are available online. Just search for ''RCT6773W22 battery'' to get results for suppliers of the part.
Here’s a link to just one [https://www.walmart.com/ip/HQRP-Battery-for-RCA-Voyager-II-7-Tablet-RCT6773W22B-RCT6773W22-Replacement-HQRP-Coaster/867869043|supplier]. It is shown only to give you an idea of the cost of the part. There are other suppliers that may suit you better.