Identifying tagging variants / haplotypes in GWAS data

Question

[Christopher]

I have been working with a GWAS dataset (n = 500), and I have identified 20 SNPs that are associated with my phenotype of interest. I would now like to use the same dataset to identify other SNPs (or Haplotypes) that can be used a proxy (r2 > 0.8) for each of these 20 SNPs.

I looking for a recommendation for a tool that can do this for haplotypes in particular; i.e. identify a 2 SNP haplotype that is a proxy (r2 > 0.8) for the index SNP