A company was formed before my involvement and although I have Memo and Arts I don't have the Register of Members, Share Certs etc. for this company.
Can I purchase these now and from where?
The register of members is usually kept at the companies registered office. The share certs may be with the Register of Members or given to the original shareholders. Probably should have been given to you if you bought the shares.
The B1 filed with the CRO should have the most recent shareholders this can be downloaded from www.cro.ie for a fee or you could ask the Company Secretary for a copy.