You can add a calculated field with the formula SUM([Purchases]) / TOTAL(SUM([Purchases])) * 100 to get the % of the total for each supplier.
Then add this new measure to your viz along with the measure [Purchases]. You can make the viz dual axis (right click on one of the measures and select the option) and then change the scale of the new axis to be from 1 to 100 and maybe make the marks for the % measure into Gantt bar type to get that 'dot' you require
Yes absolutely it is possible... Add your % of total calculation to your viz as a Column (continuous data type), and have your Supplier name and purchases as discreet data types in the Rows section
only one issue remains.
once we set all other measures as discrete, for empty values they display 'NULL' instead of showing blank cell as before. how do i solve that?