You can do this using I-PV (http://i-pv.org/). I will give an example from myosin which is one of the example on the site ( http://i-pv.org/MYOSIN2.html ). Using this tool it is possible to view the distribution of nonsynonymous mutations that has resulted in a stop codon. Alternatively you can click on any of the amino acids and see if there is a theoretically possible point mutation that can result in a stop codon.
Below video first shows the distribution of stop codons plotted from a variation file, you can click on these and it will take you to the corresponding dbSNP website; the second part shows 9 possible point mutations that can occur in a given amino acid (lysine in this example) residue and one of them is a stop codon:
First you will have to generate such graphs. You will need to locally download and extract i-pv for this.You also need to locally install perl (I recommend strawberry perl for this) and circos since i-pv depends on them. The output opens within a browser. And you can use the output in your mobile device. If you have trouble generating such a plot for your gene, let me know, I will generate one for you.
I hope this helps,
Good luck with your research,