Sequence data (including DNA-methylation) can be found in two public repositories. NCBI SRA and EBI-ENA.

You can also deposit SRA data (the raw .fastq.gz files) through GEO, to have linked processed data sets.

I'm not sure if you are looking for a specific type of BS-Seq data, but there is also microarray DNA Methylation data in GEO (Illumina Array, MeDIP, etc.).

For arrays, you can search for specific platforms within GEO: https://www.ncbi.nlm.nih.gov/geo/browse/

Otherwise, the platform is probably the sequencing technology; so, you would want to search for "BS-Seq," "RRBS," etc among the data sets: https://www.ncbi.nlm.nih.gov/geo/